By Bill Kleiman, Nachusa Grasslands, TNC
The photo above shows mostly bur oaks growing in a prairie restoration. We planted the bur oaks in 2006, but first we planted prairie in 2001. This makes the start of a savanna. The 2001 prairie planting was maturing and we decided to plant some acorns into the five year old prairie where it approached the oak woods so we would not have an abrupt prairie to oak woods edge. It worked. Those shrubs are all oaks, many bur oak. I know they are from the acorns we planted because we planted bur oak acorns and the oaks near the edge are black and white and northern red oak.
We burn this unit frequently and the nearest oak shrub shows a few stems that were top killed by fire. In another place on the preserve where we have frequent fire there is one or two small tree sized oak for every 100 oak shrubs. So frequent fire supports development of savanna. I bet these open savanna were a common sight a few centuries back.
Above photo is when I turn around and shoot the opposite direction which shows the old oak woods adjacent to this planting. Shagbark hickory, white oak, northern red oak. A cup plant in the foreground. There is very little oak recruitment in this woods in spite of a frequent fire regime.
Above is seasonal crew Stephanie in 2006. She and I used dibble bars to plant oak acorns. Bernie uses a tile probe with similar effect. I remember getting blisters on my hands as the soil of the new planting was hard and dry. A study on this same field by soil scientist Mike Konen showed that the soil became less dense about ten years after planting to prairie. It took at least five years to notice any oaks emerging.
Above is a later photo from a different planting of acorns. Our dibble bars in 2006 made just a small dent in the ground. I think we scuffed in the opening with our boots.
So to restore a savanna, try planting a prairie first, and burn it frequently.
Do you protect the young oak shrubs when conducting a prescribed burn?
No we don’t protect them
….but we do protect an occasional woody plant in small scale situations, like near our house, or near the fire break we sometimes squirt some water as we wet line.
Hey Bill, I like to think of native grassland’s and savanna as the same type of vegetation, only one label has trees (that evolved with the grasslands and herbivores, e.g., oak, aspen, hawthorn, etc.) and the other label does not have trees, and whether there is a tree in the grass is a principle of scale and not type. At UW-Madison, I still hear TF Allen say over and over again, “don’t confuse scale and type. Epistemology matters”. Anyways, this concept has helped me design and implement multiple highly successful projects in the upper Midwest over the past 15 years. In fact, my preferred term for grassland ecosystems is (grassland-savanna). I don’t use the colloquial term prairie anymore…, unless I am forced to, :). Keep up the good work, Bill. ST
I am pondering your thoughts on the word prairie. I have written the word prairie enough that my hands don’t think about which keys. I see your point.
Here are Dr. Brian Wilsey’s thoughts on the matter as expressed in his book “The Biology of Grasslands.”
“The way to answer the question of whether savannas are transitional or stable systems is to do studies that address two issues: 1) are there species that achieve their highest abundance in savannas, although they may by (sic) present in both grasslands and forests (Figure 8.9)? 2) Do grasses and trees utilize resources differently, which would enable the two growth forms to coexist indefinitely? Some people base their answer to this question on how extensive savannas are, with the assumption that a narrow band of savanna would be indicative a (sic) transitional (non-stable) system. At the wet end of the spectrum, savannas grade into forests. However, using this logic, the huge grasslands in the interior of continents would be regarded as transitional systems between forests and deserts, which clearly is not the case.”
“… Relict savannahs in the Midwestern USA are identified by locating open grown oak trees and herbaceous species that may be present in forests or grasslands (Brudvig and Asbjornsen 2007). The abundance and persistence of some species are higher in savannas than in forests or grasslands, suggestive of savannas as a persistent system. Herbaceous species in North American Midwest that fit this description include Virginia wild rye (Elymus virginicus), horse gentian (Triostemum perfoliatum), and wild petunia (Ruellia humilis). Open grown oaks with thick bark that are fire resistant like burr oak (Quercus macrocarpa) in the north and black oak and post oak (Quercus velutina and stellata) in the south are also good indicators of former savannas.”
Very nice to inform us this variety of prairie work you do. New to me. I manage a 1/2 acre savanna with old, dying burr oaks. In only a small part, enough oaks have come up on their own. In other parts I’ll plant acorns and protect them for several years, Looks like you are able to just plant a large number and see what happens over time. Do you plant a particular variety of grasses and forbs or let the savanna form itself, like prairies in general?
We have only purposely “planted a savanna” a few times. Both times we planted a diverse amount of prairie species and not woody seeds. No shrubs, no acorns. We could have planted shrubs and trees year one, but we didn’t, more for logistical reasons. We did not plant herbaceous species that would later like the shade of some future oaks. We figured that we plant prairie, and in the future when we have some patchy shade we can sprinkle in seeds of some species that might like some patchy shade, say Silene stellata.
I did not know you were working on restoring savanna. If I had known, I would have forwarded this video to you earlier. I thought it was an interesting idea.
My lawn is starting to turn into savanna. This is not because I plant acorns. The squirrels have been doing that for me. The reason I have oak trees growing in my lawn is because when I see an oak tree seedling, I put a little cage over it. That way I remember not to mow it. Some are several years old now, but still less than a foot tall.
What depth do you plant bur oak acorns?
Top of nut about an an inch under soil.